percpu-refcount: add __must_check to percpu_ref_init() and don't use... (acac7883) · Commits · 戴 / test

percpu-refcount: add __must_check to percpu_ref_init() and don't use ACCESS_ONCE() in percpu_ref_kill_rcu() Two small changes. * Unlike most init functions, percpu_ref_init() allocates memory and may fail. Let's mark it with __must_check in case the caller forgets. * percpu_ref_kill_rcu() is unnecessarily using ACCESS_ONCE() to dereference @ref->pcpu_count, which can be misleading. The pointer is guaranteed to be valid and visible and can't change underneath the function. Drop ACCESS_ONCE(). Signed-off-by:

Tejun Heo <tj@kernel.org>

include/linux/percpu-refcount.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -66,7 +66,8 @@ struct percpu_ref {
		struct rcu_head rcu;
		};

		int percpu_ref_init(struct percpu_ref ref, percpu_ref_func_t release);
		int __must_check percpu_ref_init(struct percpu_ref *ref,
		percpu_ref_func_t *release);
		void percpu_ref_kill(struct percpu_ref *ref);

		#define PCPU_STATUS_BITS 2

lib/percpu-refcount.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -57,12 +57,10 @@ int percpu_ref_init(struct percpu_ref ref, percpu_ref_func_t release)
		static void percpu_ref_kill_rcu(struct rcu_head *rcu)
		{
		struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu);
		unsigned __percpu *pcpu_count;
		unsigned __percpu *pcpu_count = ref->pcpu_count;
		unsigned count = 0;
		int cpu;

		pcpu_count = ACCESS_ONCE(ref->pcpu_count);

		/* Mask out PCPU_REF_DEAD */
		pcpu_count = (unsigned __percpu *)
		(((unsigned long) pcpu_count) & ~PCPU_STATUS_MASK);

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